Signaling system



l 1934. v R. s. BONE 1,953,462

v SIGNALING SYSTEM Filed Dec. 12, 1930 T/ R/ R2 R 3 72 RHEOSMT INVENTOR RS. BONE ATTORNEY Patented Apr. 3, 1934 UNITED STATES PATENT? Fries SIGNALING SYSTEM York Application December 12, 1930, Serial No. 501,797 In Great Britain January 1, 1930 9 Claims. (Cl. 179170) This invention relates to improvements in electrical signaling systems, and more particularly to electrical signaling systems in which automatic means are provided to maintain one or more signal characteristics within predetermined limits at a given point or points in the system.

One object of the invention is to provide a signaling system that shall prevent indiscriminate action or interaction of or between any or all of a plurality of gain control means designed to compensate for changes of signal characteristics.

Another object of the invention is to provide a signaling system having a plurality of signal characteristic correcting means that shall effect a predetermined delay in the operation of each signal characteristic correcting means, each one of the correcting means in the signaling system having a substantially diiierent period'of delay when compared with the operation of other correcting means in the system.

Another object of the invention is to provide a signaling system of the above indicated character having substantially similar delay controlling means at each signal correcting means which differ only in minor adjustments.

A further object of the invention is to provide a signaling system of the above indicated character that shall have the period of delay of each delay controlling means individually adjustable to accommodate changes in the signal characteristic due to causes which are known to be peculiar to any particular locality.

In the art of electrical signaling it is well known to provide means other than manually operated means to compensatae for variations in the signal characteristics due, for example, to transient changes in the transmission medium. As instances of the cause of signal characteristic variation, fading phenomena in radio communication and variable leakage in line communication may be mentioned.

It is further well known in the art to provide so-called automatic gain control means, so that at any given point or points in the transmission system, signal amplitude is maintained within predetermined limits. For example, a line repeater or radio receiver or any similar signal responsive device may be provided with automatic gain control means, whereby signals at the output of said devices aremaintained within predetermined amplitude limits, regardless of variations in amplitude at the input.

In a long transmission system it is known to regulate a plurality of repeaters by automatic gain control means, each of said repeaters being regulated by the preceding one, or by changes in the transmission medium in a line section preceding it. A disadvantage of such systems will be apparent from the following example.

Consider a change in the first section of the transmission medium which results in a decrease in received signal amplitude of two decibels. If the transmission system contained three repeaters, each would increase its gain by two decibels, resulting in a total increase of six decibels. The second and third repeaters would then be operating above their normal gain, and the automatic gain control means at these points would commence to step down the gain to the normal level and this stepping up and down would either continue indefinitely or until each repeater was again operating at its normal gain.

Ina system constructed in accordance with the invention various repeater stations are provided with delay controlling means which govern the time at which the gain control apparatus at the different stations start operation. Thus the gain control apparatus at the difierent repeater stations start to operate at different times and do not start to operate simultaneously. The providing or" a different time delay for the gain control apparatus at the difierent repeater stations insures against the so called hunting action.

It will be understood that the expression automatic gain control as used herein is employed for the purpose of illustration and is intended to embrace any means which function to correct changes in the characteristics of signals, regardless of the source or nature of such changes of characteristics.

One embodiment of the invention will now be described, by way of example and with reference to the accompanying drawing, as applied to the prevention of hunting in an electrical transmission system employing a plurality of repeaters with automatic gain control.

Fig. 1 showsa line transmisison system according to one embodiment of the invention, wherein a plurality of repeaters are employed, each equipped with so-called automatic gain control means;

Fig. 2 shows a circuit arrangement by means of which the period of delayed operation can be obtained; and

Fig. 3 shows an application of the invention to a two-way carrier signaling system.

Referring to Fig. 1, T1 and T2 represent the terminal equipment for the transmission system, T1 being adapted to transmit signals to T2.

Simultaneously with the signals T1 transmits, in a known manner, a pilot current which may have a frequency within the signal frequency band and which being subject to the same varying line conditions as the signals, is used as the controlling means for the automatic gain control devices at the repeaters R1, R2 and R3.

Each of the repeaters R1, R2 and R3 of Fig. 1 is equipped with delay means for delaying the operation of the said automatic gain control means, which said delay means may be of the type shown, by way of example, in Fig. 2 to-which reference will now be made. A thermionic valve V normally having a sufficiently large negative potential on its grid to prevent the flow of anode current is provided, and the incoming pilot current, after detection at H, is adapted to cause the marginal relay A to operate, whereupon another relay B opens its contact and removes the source of negative potential from connection with the grid of the thermionic valve V, and allows a condenser C to discharge through a leak resistance R. The rate at which the said discharge takes place may be varied by altering the resistance R, and in practice, this resistance would be set to meet the requirements of the time delay required at the repeater with which the delay means is associated. This determines the time delay in the operation of the gain control apparatus connected to the output terminals F by governing the time required for the plate current to build up sufiiciently to operate the relay D. The detector H may be a space discharge device as shown on the drawing or any other well known type of detector. The contact members of the relay D are connected in circuit with any suitable gain control circuit so as to prevent operation of the gain control circuit until after a predetermined delay. In Fig. 2 of the drawing is shown a gain control apparatus of the type disclosed in Fig. 3 ofthe L. Espenschied et al. Patent No. 1,447,773 dated March 6, 1923. Inasmuch as the invention is not restricted to any particular type of gain control apparatus a detailed description of the gain control apparatus is deemed unnecessary. Reference may be made to the Espenschied et a1. patent for a complete description of the gain control apparatus shown. Other types of gain control apparatus which may be used with the invention are shown in the patent to J. S. Jammer No. 1,623,600 dated April 5, 1927, and the patent to H. A. Ariel No. 1,468,687 dated September 25, 1923.

In accordance with one of the features of the invention, each of the said repeaters has a different period of delayed operation. Consider, then that each of the said repeaters can have its gain increased from minimum to maximum in two seconds, and that the time delay device for repeater R1 (Fig. 1) is so adjusted that the gain control operates five seconds after a disturbance has occurred in the first line section between T1 and R1. Under these conditions the gain of R1 will be varied from minimum to maximum in a period of seven seconds from the occurrence of the disturbance. Now, if repeater B2 has its associated time delay device so adjusted that a period of 7 /2 seconds must elapse between the occurrance of a disturbance and the operation of its gain control means said gain control will operate only if the gain adjustment due to R1 has not been sufiicient to eliminate the effects of the disturbance, and thus hunting between the repeaters R1 and R2 will be eliminated.

It will be clear that repeater R3 may have a delayed operation period of, for example, 10 seconds, and that in a signaling system employing a larger number of repeaters than the three shown by Way of illustration, each of the repeaters in the system will have a different period of delay.

Referring to Fig. 3, which shows an embodiment of the invention as applied to a.two-way carrier system, it will be clear that, from the point of view of the timing of the delay devices, the repeaters R7, R6 and R9 for the direction east to west, for example, should be regarded as a one-way transmission system, giving R9 the longest delay period, and for the direction west to east, repeaters Rm,- R11 and R12 should be regarded as another one-way system, giving R12 the longest delay period.

It should be understood that the invention contemplates the use of other timing devices than that chosen as an example. Any convenient time delay device may be employed such as thermal slow acting relays or other known timing devices. For instance, a bi-metal strip type of thermostat may be employed, the necessary heating current being derived from the pilot current. The said bi-metal strip will be arranged to reach a contact when the heating current has been applied for a time dependent upon the delay period required.

It should be further understood that the pegain could be restored in 2 seconds, and the motor i at R2 ran at such a speed that the normal gain at this repeater was restored in 5 seconds, hunting would be impossible because R would have reached its normal gain condition and become stable before R2. to step up or down only to the limit set by the pilot current from the how normal R1. To ensure complete absence of hunting, the motors would be set at such speeds that the gain of any preceding repeater could be varied from minimum to maximum and back to minimum before a successive repeater reached a normal gain condition, since the condition of normal gain must exist within the limits of the total range of adjustment of the gain control device. By this means, a preceding repeater can reach normal gain, regardless of the potentiometer setting required, before a successive repeater can commence hunting for the normal gain condition.

Although this invention has been described as being applicable to the prevention of hunting in gain controlled repeaters, it is contemplated that there are many other applications of the invention within its scope, such as the prevention of hunting in automatic phase correcting devices in electrical signal systems, or in connection with any series of devices which serve to automatically restore signals to a predetermined form.

What is claimed is:

1. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said stations to compensate for changes in a characteristic of the signals on said line, and control means for preventing the operation of said compensating means at For R2 would therefore continue 1 the repeater stations until a predetermined time interval after a change in the characteristic of the signals on the line, said control means operating to insure the time taken to restore a signal to a predetermined form at any station being substantially different from that of any other station.

2. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said stations to compensate for changes in a characteristic of the signals on said line, and control means for preventing the operation of said compensating means at the repeater stations until a predetermined time interval after a change in the characteristic of the signals and for insuring the time periods taken at the various repeater stations to restore a signal on the line to a predetermined form to progressively increase in the direction of transmission.

3. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said stations to compensate for changes in a characteristic of the signals on the line, and control means for preventing the operation of said compensating means at the repeater stations until a predetermined time interval after a change in the characteristic of the signal and for insuring that the compensating means at any repeater station performs its compensating function and restores the signals to a predetermined form before the compensating means at any successive repeater station commences its compensating function.

4. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said stations to compensate for changes in a characteristic of the signals on the line, and control means at the various repeater stations for timing the operation of the compensating means at the various repeater stations so that the compensating means at any precedirn repeater station performs its compensating function and restores the signals to a predetermined form before the compensating means at any successive repeater station completes its compensating function.

5. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said repeater stations to compensate for changes in a characteristic of the signals, and control means comprising a thermionic valve system modifying the compensating means at each repeater station for effecting different periods of delay in the operation of the compensating means at the different repeater stations.

6. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at each of said stations comprising a motor operated rheostat to compensate for changes in a characteristic of the signals on the line, and means for automatically controlling the time of operation of the compensating means at the various stations by operating the motor operated rheostats at different speeds.

7. In a signaling system, a plurality of repeater stations, means at said stations to compensate for changes in a characteristic of the signals, and means for determining the time of operation of the compensating means comprising a first relay in combination with a capacity element, a resistance element, a thermionic valve and a second relay in the anode circuit of said thermionic valve, in such relation that said first relay places the said thermionic valve in an operative condition, and causes said capacity element to discharge into the input circuit of said thermionic valve, the period occupied by the said discharge being a function of the relation between said capacity element and said resistance element, while the said period governs the time taken for the anode current of the thermionic valve to change sufficiently to operate said second relay.

8. An electrical signaling system comprising a plurality of repeaters for transmission in one direction and a plurality of repeaters for transmission in the opposite direction, said repeaters being adapted to be influenced by gain controlling means, said means being eifective only if the energy level departs from a predetermined value for a predetermined time, characterized in this that each of said repeaters adapted for transmission in one direction has a different time lag period from other repeaters adapted for transmission in the same direction, and that each of said repeaters adapted for transmission in the opposite direction to the first said repeaters has a different time lag of operation from other repeaters adapted to transmit in the said opposite direction, the said time lags progressively increasing in the direction of transmission.

9. In a signaling system, a plurality of repeater stations, a transmission line connecting said repeater stations, means at said repeater stations to compensate for changes in a characteristic of the signals on the line, and means for effecting time delays of different intervals in the operation of the compensating means at the various repeater stations to prevent hunting action between any of the compensating means at said repeater stations.

RONALD SCOBLE BONE. 

